The present invention relates to a carburetor for an internal combustion engine, and more particularly to such a carburetor which can control fuel, in quantity, fed to the engine in accordance with accelerating conditions.
Usually carburetors are desired to be provided with a fuel enrichment device, such as an acceleration pump, to meet acceleration demands. The acceleration pump is usually operatively connected with and controlled by a carburetor throttle valve in such a manner that upon acceleration, the quantity of fuel fed by the pump to the engine is controlled in response to "throttle opening degree difference," that is; a difference, in opening degree of a carburetor throttle valve, between initial position of the throttle valve before acceleration and final position of the throttle valve after such acceleration.
If such an acceleration pump is set so as to feed enough quantity of fuel to the engine required upon acceleration with small throttle opening degree difference at low speeds, an overabundance of fuel will be fed to the engine upon acceleration with large throttle opening degree difference at high speeds increasing HC and CO emissions, and thus fuel consumption upon this acceleration becomes great. While, if the pump is set so as to feed enough quantity of fuel to the engine required upon acceleration with large throttle opening degree difference at high speeds, quantity of fuel fed by the pump to the engine upon acceleration with small throttle opening degree difference at low speeds will be small and not enough for the acceleration demand thus degrading driveability.